1. Field of the Invention
The present invention relates to a video signal processing device which processes a video signal for stereoscopic display, a display device which displays the processed video signal, a display method which is applied to a display process in the display device, and a program product which executes the display method.
2. Description of the Related Art
In the related art, in a case where video signals for a stereoscopic display (3D display) are supplied to and displayed on a display device such as a monitor display, video signals for a left channel and video signals for a right channel are supplied to the display device. Videos based on the video signals for the respective channels are separately viewed by the left and right eyes of a person viewing the display device.
For example, the person viewing the display device wears a glasses-type liquid crystal shutter device in which shutters for the right eye and the left eye are alternately opened and closed for each frame. Further, a video for the left channel and a video for the right channel are alternately displayed on the display device for each frame, and the shutters for the left and right eyes are alternately opened and closed for each frame, thereby recognizing the videos based on the video signals for the respective channels with the left and right eyes. On the other hand, there is a type of generating a stereoscopic vision by a process in a display device without wearing special glasses or the like. As display methods, there are various methods, in addition to the above-described method of changing videos for the left channel and videos for the right channel for each frame, for example, a method of changing videos for the left and right channels for each horizontal line.
In order to implement such a stereoscopic vision, it is necessary to use a dedicated display device for a 3D display; however, when capturing is performed using a camera device, there are many environments where the dedicated display device for a 3D display is not used. In this case, a video for a left channel and a video for a right channel are input to the display device, and the two input videos based on video signals are alternately changed, displayed and viewed.
FIG. 8 is a diagram illustrating a configuration of an image processing device 10 which alternately changes and supplies videos for two channels to a display device in the related art. In FIG. 8, an image processing device 10 and an image display device 20 are shown as a separate body, but may be formed as a single body. The image processing device 10 includes a first input terminal 11 and a second input terminal 12, and supplies video signals input to both the input terminals 11 and 12 to a video changing unit 13. The video changing unit 13 includes a switch, supplies a signal input to the first input terminal 11 to a first contact point 13a, supplies a signal input to the second input terminal 12 to a second contact point 13b, and selects a signal at either of the two contact points using a movable contact point 13m. The change in the switch is performed under the control of a CPU 14 which is a control unit.
The video signal selected by the video changing unit 13 is supplied to a video signal processing circuit 15 and a synchronization separating circuit 16. The video signal processing circuit 15 processes a video (image) part of the video signal so as to be appropriately displayed. The processed video signal is supplied to the image display device 20.
The synchronization separating circuit 16 separates synchronization signal components from the supplied video signal, and supplies the separated synchronization signal components to the image display device 20. The image display device 20 displays videos (images) in synchronization with the synchronization signal components.
The synchronization signals separated by the synchronization separating circuit 16 are supplied to a signal determination circuit 17 which determines synchronization timings and supplies the determined result to the CPU 14. The CPU 14 makes the video changing unit 13 change the video signals in synchronization with the determined timings.
Under the control of the CPU 14, when the video changing unit 13 changes a video signal to another type of video signal, in order to prevent the displayed videos from looking untidy during the change, a process called an image mute is temporarily performed. In the image mute process, for example, if a first video signal is assumed to be changed to a second video signal, a last frame of the first video signal is displayed, and thereafter an entirely black image is displayed during a period of one frame or several frames. After the entirely black image is displayed, a video based on the second video signal is displayed.
FIG. 9 is a diagram illustrating an outline of this display state. While the first input video is changed to the second input video, an entirely black image for the image mute is displayed during at least one frame period.
This image mute process is a generally performed technique during the change of channels, external inputs, or the like, even in a case of a display device such as, for example, a television set.
Japanese Unexamined Patent Application Publication No. 3-191682 discloses an example of the television set which performs the image mute process.
On the other hand, if the image mute process is performed during the general video change, in a display type where videos for left and right channels used to implement stereoscopic vision are alternately displayed using a single display device, the display of the videos for stereoscopic vision is hindered in some cases.
In other words, for example, in a case where a video for the left channel and a video for the right channel are alternately displayed on one screen, if the entirely black image for the image mute is displayed once every video change, the videos for the left and right channels may not be compared rapidly. Particularly, if videos for two channels are alternately changed at a relatively short cycle, a period when the entirely black image is displayed is lengthened, and thus the displayed videos appear very untidy.